CN1172017C - Ferritic stainless steel with excellent machinability and production thereof - Google Patents
Ferritic stainless steel with excellent machinability and production thereof Download PDFInfo
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- CN1172017C CN1172017C CNB011369132A CN01136913A CN1172017C CN 1172017 C CN1172017 C CN 1172017C CN B011369132 A CNB011369132 A CN B011369132A CN 01136913 A CN01136913 A CN 01136913A CN 1172017 C CN1172017 C CN 1172017C
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/002—Heat treatment of ferrous alloys containing Cr
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0273—Final recrystallisation annealing
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
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Abstract
The newly ferritic stainless steel sheet consists of C up to 0.03 mass %, N up to 0.03 mass %, Si up to 2.0 mass %, Mn up to 2.0 mass %, Ni up to 0.6 mass %, 9-35 mass % Cr, 0.15-0.80 mass % Nb, and the balance being Fe except inevitable impurities, comprises metallurgical structure involving precipitates of 2 mum or less in particle size at a ratio not more than 0.5 mass % and has crystalline orientation on a rolled surface at 1/4 depth of thickness with Integrated Density defined by the formula (a) not less than 1.2. The ferritic stainless steel sheet is manufactured by 25 hours or shorter precipitation-treatment at 700-850 DEG C in prior to 1 minute or shorter finish-annealing at 900-1100 DEG C. Integrated Intensity=[I(222)/I0(222)]/[I(200)/I0(200)] (a), wherein, I(222) and I(200) represents diffraction intensities on (222) and (200) planes of a sample of said steel measured by XRD, while I0(222) and I0(200) represents diffraction intensities on (222) and (200) planes of a non-directional sample.
Description
Technical field
The present invention relates to a kind of ferritic stainless steel than less anisotropy of having with excellent machinability, it can be used as the sheet material that is used for automobile and other part.
Background technology
Many fields have been widely used in by stablize the ferritic stainless steel that C and N improve thermotolerance and erosion resistance with Nb or Ti.For example, this ferritic stainless steel is as the element of automobile exhaust system.Comprise Nb or Ti to suppress sensibilized and to improve the steel of intergranular erosion resistance such as SUS409L, SUS436L or SUS436J1L are used as good pipe core or the sourdine of corrosion resistance nature.Steel SUS430LX, SUS430J1L or SUS444 are as good exhaust-gas receiver or the preceding pipe of thermotolerance, and these steel comprise Nb or the Ti above C and N stoichiometric ratio, because Nb or Ti dissolving are excessive in steel matrix, have improved hot strength.
At present, the exhaust system shape that is designed to become increasingly complex has become a kind of trend to save the space and to improve waste gas efficient.Because the shape of this complexity, ferritic stainless steel should have better processing characteristics, even also defective should not take place behind gross distortion.
The requirement of processing characteristics is not only is used for exhaust system, also be used for other application scenario.That is, be function and/or the design that improves product, along with shape of product is more complicated, ferritic stainless steel will be out of shape under heavier load.
At present the whole bag of tricks has been proposed to improve the processing characteristics of ferritic stainless steel.These suggestions belong to basically to be carried out suitable control and carries out suitable control to creating conditions its composition.
The alloy designs of No. 29694/1976 and No. 35369/1976 patent announcement proposition of Japan has reduced the content of C and N, and has increased the element that forms carbonitride with relatively large ratio, as Ti or Nb.Adding Ti and/or Nb are intended to improve the operation of processing characteristics and system requirements with the element as exhaust system in ferritic stainless steel, because additive Ti and Nb can improve the processing characteristics of steel, and for the element that is used for exhaust system, improve necessary erosion resistance and thermotolerance.
Really can improve deep-draw ductility by adding Ti and/or Nb, still increase in the plane that Ti and Nb but make the r value anisotropy value Δ r appearance and do not wish that the change that takes place is big by the r value representation.Under this kind situation, only add this alloying element and be not sufficient to make ferritic stainless steel to have enough processing characteristicies, to satisfy requirement to gross distortion.
For improving processing characteristics, knownly also can add among Al, B and the Cu one or more.
Various relevant methods of suitably creating conditions had been proposed already, from making the steel step to cold rolling or final annealing step.For example, the dull and stereotyped steel of as cast condition is to the distortion of equiaxed crystal structure, the reduction of initial temperature, soaking steel band under optimal temperature, reduction finishing temperature and the roll coil of strip temperature that is reduced in the hot-rolled step in system steel step.These temperature controls often combine with the control of reduction ratio to be carried out.Control to the frictional coefficient between steel band and work roll in course of hot rolling also can improve processing characteristics effectively.The purpose of all these methods all is to destroy the blank as-cast structure, and the blank as-cast structure can produce injurious effects to recrystallization.
Even in the step after hot-rolled step, increase cold rolling rate and also can improve the r value effectively, reduce anisotropy value Δ r in the plane simultaneously, as described in following document: " stainless steel handbook " (by Japanese stainless steel association edit and by Nikkan Kogyo ShimbunCo. in 1995 issues), the 935th page.The cold rolling rate of Ti-steel alloy must be measured with the value that surpasses 60% (preferred 70-90%).Cold rolling condition and annealing conditions or with the various combinations of bigger work roll in twice cold rolling-twice annealing also can improve processing characteristics effectively.For example, having added the steel of forming based on SUS430 of a spot of alloying element and the steel of forming based on SUS430 that add Al and Ti therein is the steel that improve processing characteristics by creating conditions.
But, as described in No. 17519/1994 patent announcement of Japan and No. 311542/1996 patent disclosure, seldom reported in literature has only the been arranged research of creating conditions for the ferritic stainless steel that is used for corrosion-resistant or heat-stable Ti or Nb alloying extends to the knowledge by " one of Ti and Nb or two " representative.These methods that propose at present need increase addition thereto or change manufacture method inevitably in conventional manufacture method, cause increasing the cost of manufacturing cost and the finished product.
For thickness is the ferrite stainless steel of 0.7-0.8mm, has studied it and has created conditions to the effect of processing characteristics, still, for the ferrite stainless steel of thickness above 1.0mm, also not clear to the effect of its processing characteristics.Use according to reality, thickness is the element that the steel plate about 2mm is widely used as the exhaust system that is used for automobile.When aforesaid method was applied to make the method for stainless steel plate of this thickness, hot rolled strip must be thicker than 6mm, surpasses 70% to realize cold rolling rate.As a result, hot-rolled steel sheet must carry out cold rolling with big load, and is stable by low-temperature flexibility and crooked sex transmission simultaneously, thereby raise its manufacturing cost inevitably.
In brief, still have the Ti of excellent processing characteristics or the ferritic stainless steel of Nb-alloying even require consumingly to provide when ferritic stainless steel is rolled into when thickness surpasses the bar of 1.0mm, it does not need additional measure or increase manufacturing cost.
Summary of the invention
The present invention aims to provide the improved ferrite stainless steel of a kind of processing characteristics, be to have utilized the precipitate that contains Nb control action kou to crystalline orientation, need not to reduce to erosion resistance or the deleterious element of thermotolerance or increase erosion resistance or the effective special elements of thermotolerance, and unrestricted to thickness.The thin existence that contains the Nb precipitate has to improvement also that anisotropic processing characteristics is effective in the low degree in steel matrix.
The present invention newly provides two types the ferrite stainless steel with excellent processing characteristics.
The first string relates to a kind of ferrite stainless steel, it is by the C of 0.03 quality % at the most, the N of 0.03 quality % at the most, the Si of 2.0 quality % at the most, the Mn of 2.0 quality % at the most, the Ni of 0.6 quality % at the most, the Cr of 9-35 quality %, 0.15-0.80 the Nb of quality % forms, all the other are iron and unavoidable impurities, comprise to have the metallographic structure that particle diameter is 2 μ m or littler precipitate, and the ratio of described precipitate is no more than 0.5 quality %, and have crystalline orientation on a surface at 1/4 thickness place, its integrated intensity by formula (a) definition is not less than 1.2.
Integrated intensity=[I
(211)/ I
0 (211)]/[I
(200)/ I
0 (200)] ... (a)
Wherein, I
(211)And I
(200)(211) and (200) planar diffracted intensity of the described steel sample that expression is recorded by XRD (X-ray diffraction), and I
0 (211)And I
0 (200)(211) and (200) planar diffracted intensity of representing nondirectional sample.
Ferrite stainless steel can further comprise one or more in the following composition: the Ti of 0.5 quality % at the most, the Mo of 3.0 quality % at the most, the Cu of 2.0 quality % and the Al of 6.0 quality % at the most at the most.Ferritic stainless steel can be the hot rolled strip that is provided by market, hot-rolled steel sheet, cold-rolled steel strip, cold-rolled steel sheet or Welded Steel Pipe.Term in this specification sheets " steel plate " comprises all these materials.
Ferrite stainless steel is by following method manufacturing: described method be included in 900-1100 ℃ carried out 1 minute or the shorter time final annealing before under 700-850 ℃, separate out and handled 25 hours or the step of shorter time.
Second scheme relates to and has anisotropic ferrite stainless steel in excellent processing characteristics and the low degree.This stainless steel plate has foregoing composition, comprise and comprise the metallographic structure that particle diameter is 0.5 μ m or littler thin precipitate, under the final annealing state, controlling its ratio and be no more than 0.5 quality % by dissolving thin precipitate, described thin precipitate is by adding thermogenesis in the final annealing process in steel matrix, have crystalline orientation, its integrated intensity by formula (b) definition is not less than 2.0.
Integrated intensity=[I
(222)/ I
0 (222)]/[I
(200)/ I
0 (200)] ... (b)
Wherein, I
(222)And I
(200)Diffracted intensity on (222) and (200) plane of the described steel plate sample that expression is recorded by XRD, and I
0 (222)And I
0 (200)(222) and (200) planar diffracted intensity of representing nondirectional sample.
Contain the thin precipitate of Nb by control, remained on by the integrated intensity of formula (b) definition and be not less than 2.0, described thin precipitate produces by heat-treating before final annealing, and content range is 0.4-1.2 quality %.
This ferritic stainless steel be by in any step before final annealing to steel with specific composition 450-750 ℃ carried out 20 hours or shorter time add heat evolution, in the final annealing process, carried out 1 minute or shorter time annealing and making then at 900-1100 ℃.
Description of drawings
Fig. 1 has shown in the effect of the precipitate that distributes in steel matrix before the final annealing to the mean strain ratio of the steel plate of final annealing.
Fig. 2 has shown at the thin precipitate that distributes in steel matrix before the final annealing the mean strain of the steel plate of final annealing anisotropic effect in the plane when.
Embodiment
The present inventor has studied composition in all its bearings and has created conditions to the effect of processing characteristics, suppose to comprise one or both and its ratio among Nb and the Ti to be enough to stablize C and N be that the ferritic stainless steel of carbonitride is to carry out cold rollingly under the 50-60% at draft that this is counted as usually and is not enough to increase numerical value r.In research process, the present inventor finds, any stage that the ferritic stainless steel of Nb-alloying can be before carrying out final annealing produces precipitate by steel plate or the steel band that thermal treatment is processed to have excellent machinability.
Based on the effect of newfound precipitate, even the present invention can produce the stainless steel plate that also has excellent processing characteristics when its thickness surpasses 1.0mm.
Handle the precipitate produce and demonstrate quantitative effect by before final annealing, separating out the ferrite stainless steel processing characteristics.For example, it is 2 μ m or less than the overall proportion of the precipitate of 2 μ m and the relation between the ferrite stainless steel processing characteristics that Fig. 1 demonstrates at particle diameter, described steel plate is to make like this: with thickness is that the 12Cr-0.8Mn-0.5Si-0.6Nb steel plate of 4.5mm carries out separating out in 30 seconds processing and is 2.0mm and carries out final annealing under 1040 ℃ to generate precipitate, to be cold-rolled to thickness.The unexpected increase sign of average plastic strain ratio r is that the overall proportion of the precipitate of 2 μ m or the precipitate that is lower than 2 μ m increases at the particle diameter that surpasses 1.1 quality %.Integrated intensity by above-mentioned formula (a) expression also increases to 1.2 or bigger, and increases corresponding to average plastic strain ratio r, and ferrite stainless steel is shaped as the desired shape with excellent machinability.
According to The above results, be appreciated that integrated intensity by formula (a) definition should remain on to be not less than 1.2 that to obtain to have the ferritic stainless steel of excellent machinability, in other words, mean value r is 1.5 or bigger.Integrated intensity be 1.2 or bigger be by be manufactured on overall proportion be 1.1 quality % or when bigger particle diameter be 2 μ m or littler precipitate.The overall proportion of precipitate preferably remains on relatively low level in the specified range, because precipitate is the starting point as brittle rupture, though, control optional to the overall proportion of its precipitate under the final annealing state for being not the stainless steel plate of of great value element as toughness.
Be no more than 0.5 quality % by the ratio that is controlled at 0.5 μ m in the steel behind the final annealing or littler thin precipitate and can realize having excellent machinability than under the anisotropy in the low degree.
For example, the 14Cr-1Mn-1Si-0.4Nb-0.1Cu steel is processed to the hot-rolled steel sheet that thickness is 4.5mm, heats to generate thin precipitate in 30 seconds, and being cold-rolled to thickness is 2.0mm, carries out final annealing then under 1040 ℃.Under this condition, change is separated out treatment temp and is separated out the influence that processing generates thin precipitate with research.
Processing characteristics to the final annealing steel plate detects, and is that the overall proportion of 0.5 μ m or littler thin precipitate is classified according to particle diameter, and described precipitate is present in the steel matrix that carries out before the final annealing.Estimate processing characteristics by the peaceful intra-face anisotropy Δ of average r value r value.The result wherein, is also pointed out by the integrated intensity of formula (b) definition as shown in Figure 2.
Result shown in Figure 2 confirms that particle diameter is that 0.5 μ m or the littler increase of thin precipitate in overall proportion will cause that above 0.4 quality % average r value increases peaceful intra-face anisotropy Δ r value and reduces.Thin precipitate increase also can cause integrated intensity to increase.In ferritic stainless steel demonstrated the scope of excellent machinability, integrated intensity remained on 2.0 the level of being no more than.On the other hand, the thin precipitate that overall proportion surpasses 1.2 quality % can cause the reduction of anisotropic unexpected increase and integrated intensity on the plane in, though no matter carefully the ratio of precipitate how, mean value r all can not reduce.
According to The above results, be appreciated that integrated intensity by formula (b) definition should remain on to be not less than 2.0, so that ferritic stainless steel has good processing properties, in other words, average r value should be 1.2 or bigger, and anisotropy value Δ r is 0.5 or littler in the plane.Integrated intensity be 2.0 or the bigger particle diameter that is achieved in that generation be that the scope of the overall proportion of 0.5 μ m or littler thin precipitate is 0.4-1.2 quality %.In alloy system of the present invention, preferably the overall proportion with thin precipitate remains on the relatively low level, in 0.4-1.2 quality %, because precipitate is the starting point as brittle rupture, though for being not the stainless steel plate of of great value element as toughness, it is nonessential that its overall proportion of thin precipitate under the final annealing state is controlled.In the final annealing step, by making thin precipitate dissolving to guarantee the toughness of ferrite stainless steel, being used to control the growth of aggregate structure by it, is that the overall proportion of 0.5 μ m or littler thin precipitate reduces to 0.5 quality % or littler behind final annealing thereby reduce particle diameter.
It is not fully aware of that processing characteristics changes relevant with the precipitate overall proportion, but the present inventor has imagined precipitate to the active following reason of processibility: hot rolled strip or steel formability become metallographic structure, wherein, by annealing being lower than under the temperature of its recrystallization temperature, make a large amount of Nb precipitates that contain that distribute.In alloying system of the present invention, the precipitate that contains Nb is based on Fe
3Nb laves phases and based on Fe
3Nb
3The carbonitride of C.During final annealing, this precipitate has promoted the preferential formation of (211) and (222) plane aggregate structure, has improved processing characteristics effectively, but stops the growth to processing characteristics deleterious (200) plane aggregate structure.As a result, the steel plate after the annealing has good processing properties.
Guarantee the toughness of ferrite stainless steel by the dissolving precipitate, this is used for being controlled at the growth of final annealing step aggregate structure, thereby behind final annealing, reduce by 2 μ m or littler, preferred 0.5 μ m or more the overall proportion of the precipitate of small particle size be reduced to 0.5 quality % or littler.
The ferritic stainless steel that newly provides has following composition:
Each is at most 0.03 quality % C and N
Though C and N are generally the element that improves hot strength such as creep strength,, excessive adding C and N not only can make erosion resistance, scale resistance, processing characteristics and toughness variation, and the content that must increase Nb is carbonitride to stablize C and N.In this case, the content of C and N preferably is adjusted to low-level.The content of C and N is controlled in and is no more than 0.03 quality % (preferred 0.02 quality %).
Si is 2.0 quality % at the most
Si is a kind of alloy element that can improve scale resistance at high temperature very effectively.But excessive adding Si will cause hardness to increase and make processing characteristics and toughness decline.Under this meaning, Si content should be adjusted to and be no more than 2.0 quality % (preferred 1.5 quality %).
Mn is 2.0 quality % at the most
Mn is a kind of alloy element that is used to improve high temperature scale resistance and iron scale separability, and still, excessive adding Mn will produce injurious effects to weldability.And then, excessive adding Mn, it is the austenite stable element, can promote to generate martensitic phase, causes processing characteristics to descend.Therefore, the upper limit of Mn content is defined as 2.0 quality % (preferred 1.5 quality %).
Ni is 0.6 quality % at the most
Ni is a kind of element of stable austenite phase, thereby excessive adding Ni will promote to generate martensitic phase and make poor processability as Mn.Ni also is a kind of element of costliness.On this meaning, the upper limit of Ni content is defined as 0.6 quality % (preferred 0.5 quality %).
The Cr of 9-35 quality %
Cr is a kind of stable ferritic phase, the scale resistance when high temperature uses, and essential anti-tubercular corrosion and the bioelement of weathering resistance when being used for corrosive environment.Along with Cr content increases, thermotolerance and erosion resistance are all better, and still, excessive adding Cr will cause steel to become fragile and hardness increases, and cause poor processability.Therefore, Cr content should be controlled at 9-35 quality % (preferred 12-19 quality %).
0.15-0.80 the Nb of quality %
Usually, Nb can stabilize to carbonitride with C and N, and remaining Nb can improve the hot strength of steel.And then, add the recrystallization aggregate structure that Nb is used to control steel of the present invention.By Nb is dissolved in the matrix of hot-rolled steel sheet, guarantee the generation of thin precipitate.
Being used for stablizing C and N adds Nb as the part that carbonitride consumed (C, N) form exists, and to the final annealing step, can not change its form or its ratio by hot-rolled step basically with Nb.On the other hand, another part is dissolved in the Nb that adds in hot rolled strip or the steel plate and handled and with Fe by separating out before carrying out final annealing
3Nb
3C, Fe
2Nb etc. separate out, and precipitate has advantageously been controlled the preferred growth of the recrystallization aggregate structure that is used to improve processing characteristics effectively.Under this meaning, the ratio of Nb should remain on and be higher than and C and N must be stabilized to the necessary ratio of carbonitride.Therefore, the lower limit of Nb content is defined as 0.15 quality % (preferred 0.20 quality %).But the ratio that should control Nb is no more than 0.80) quality % (preferred 0.50 quality %), generate too many because excessive adding Nb will cause to the deleterious precipitate of toughness.
Ti is 0.5 quality % at the most
Ti is a kind of selective element, and it is the same with Nb can to stabilize to carbonitride with C and N, and can improve the intergranular erosion resistance.But excessive adding Ti will make the toughness and the poor processability of steel, and the outward appearance of steel plate is produced injurious effects.Under this meaning, the upper limit of Ti content is defined as 0.5 quality % (preferred 0.3 quality %).
Mo is 3.0 quality % at the most
Mo is a kind of element that improves erosion resistance and thermotolerance (comprising hot strength and high temperature scale resistance), therefore, Mo is optionally added in the steel that needs excellent properties.But excessive adding Mo will make hot rolling, processing characteristics and the toughness variation of steel, also can increase the cost of steel.Under this meaning, the upper limit of Mo content is defined as 3.0 quality % (preferred 2.5 quality %).
Cu is 2.0 quality % at the most
Cu is a kind of selectivity alloy element that improves erosion resistance and hot strength, also gives ferritic stainless steel and has anti-microbial properties.But excessive adding Cu can cause hot rolling degradation, processing characteristics and the toughness variation of steel.Under this meaning, the upper limit of Cu content is defined as 2.0 quality % (preferred 1.5 quality %).
Al is 6.0 quality % at the most
Al is the selectivity alloy element that a kind of be used to the same with Si improves ferritic stainless steel high temperature scale resistance.But excessive adding Al will cause the increase of steel hardness and processing characteristics and toughness variation.Under this meaning, the upper limit of Al content is defined as 6.0 quality % (preferred 4.0 quality %).
The ratio of other element is not carried out particular restriction in the present invention, but one or more these other elements can add according to specific requirement.For example, Ta, W, V and Co can be used for hot strength, and Y and REM (rare earth metal) are used for the high temperature scale resistance, and Ca, Mg and B are used for hot workability and toughness.The ratio of Ta, W, V and/or Co preferably is at most 3.0 quality %, and the ratio of Y and/or REM is 0.5 quality % at the most preferably, and the ratio of Ca, Mg and/or B is 0.05 quality % at the most preferably.
The content of common impurities such as P, S and O preferably is controlled at low as far as possible.For example, P is no more than 0.04 quality %, and S is no more than 0.03 quality % and O is no more than 0.02 quality %.These impurity as far as possible strictly are controlled at lower numerical value, with processing characteristics and the toughness of improving steel.
Creating conditions of first type stainless steel plate
With ferrite stainless steel 700-850 ℃ down heating 25 hours or shorter time in steel matrix, to separate out the particle that contains Nb.Adopt continuously or the batch-type annealing furnace, before the final annealing step, separate out processing from any stage that system steel step begins.It is 2 μ m or littler precipitate to the particle diameter of the effective suitable proportion of processing characteristics that the condition of separating out processing is controlled at generation.
The particle diameter that is not less than 1.1 quality % by the generation overall proportion is 2 μ m or littler precipitate, has significantly improved the processing characteristics of stainless steel plate.Particle diameter is that 2 μ m or littler precipitate are that heating generates under 700 ℃ or higher temperature, but the heating furnace temperature surpasses 850 ℃ of precipitate growths that will cause particle diameter greater than 2 μ m.On the other hand, when heating under being lower than 700 ℃ temperature, particle diameter is that the generation of 2 μ m or littler precipitate is insufficient.
Separate out the treatment time suitable by Heating temperature T (℃) decide.In fact, determine that time t and Heating temperature T are 19-23 to keep the λ value by the following formula definition.Separating out processing should finish in 25 hours; Otherwise because long-time heating, precipitate can be grown to serve as coarse particles, brings underproductivity.
λ＝(T+273)×(20+log t)/1000
By separating out processing, particle diameter is that 2 μ m or littler precipitate distribute in the proper ratio, and the stainless steel plate of such metallographic structure carries out final annealing and recrystallization under 900-1100 ℃, reduces rolled structure.Recrystallization takes place under 900 ℃ or higher annealing temperature, still, will speed up the coarse crystallization particulate and generates being higher than 1100 ℃ of following overannealings, makes the toughness variation of steel plate.According to throughput and energy expenditure, final annealing was preferably finished in 1 minute.
It is that the overall proportion of 2 μ m or littler undissolved precipitate is brought down below 0.5 quality % that the condition of final annealing is controlled at particle diameter, to improve toughness (particularly capacity to reprocess).If precipitate remains in the product made from steel of final annealing attitude too much, then they can play the effect of brittle rupture starting point.
The recrystallization that takes place in the final annealing process is the precipitate effect that is contained Nb.That is to say, (211) plane aggregate structure preferred growth, and the growth of (100) plane aggregate structure is suppressed.As a result, the integrated intensity by above-mentioned formula (a) definition increases to 1.2 or bigger.Because integrated intensity increases, the stainless steel plate processing characteristics behind the final annealing improves, and its average plastic strain ratio r is 1.5 or bigger.
Creating conditions of second type stainless steel plate
Any stage before final annealing is in 450-750 ℃ of following heating ferrite stainless steel, to separate out the thin Nb particle that contains in steel matrix.The condition of separating out processing should be controlled at and make particle diameter is 0.5 μ m or the littler distribution of precipitate in steel matrix, and its overall proportion is not less than 0.4 quality %.If steel heats being lower than under 450 ℃ the temperature, then almost can not generate thin precipitate.In contrast, if steel heats being higher than under 750 ℃ the temperature, then precipitate grows into the coarse particles of particle diameter greater than 0.5 μ m.
Grow into coarse particles for suppressing precipitate, the time that ferritic stainless steel heats under specified temp should be shorter than 20 hours.Do not do particular restriction in the present invention though separate out the temperature and the combination of heat-up time of processing, it is that 13-19 is to stablize the character of ferritic stainless steel that heating condition preferably is defined as keeping above-mentioned λ value.
Then, with ferritic stainless steel at 900-1100 ℃ of following final annealing 1 minute or shorter.If the temperature of final annealing is lower than recrystallization temperature, then the ladle after the annealing contains a kind of tissue, wherein, handles the not fully dissolved rolled structure existence of thin precipitate that produces by separating out.Remaining rolled structure can anisotropy produces obstruction in the plane to reducing, and simultaneously, remaining precipitate makes the toughness and the suitability for secondary processing degradation of product made from steel.But superheated also can cause grain coarsening when being higher than 1100 ℃, causes toughness not enough.
Should be controlled at by the integrated intensity of above-mentioned formula (b) definition is 2.0 or bigger, thereby guarantees (222) plane aggregate structure preferred growth, to obtain good processing properties and low anisotropy.
Hot rolled strip is being used for separating out processing before the final annealing of recrystallization, and creating conditions of other needn't limit.For example, steel band can cold rolling one or many, but should not be heated to recrystallization temperature in the step except that final annealing.Especially, under twice or repeatedly cold rolling situation, should under being lower than recrystallization temperature, carry out the de-stressing after the cold rolling step, thereby suppress to generate the recrystallization tissue.Hot-rolled condition does not have particular restriction, avoids recrystallization because carry out the hot rolling meeting under 800-1250 ℃ conventional temperature.Immediately with water cooling and then coiled pipe cooling, in steel matrix, can not generate thin precipitate as hot rolled strip.In this case, the processing of separating out that is used to generate thin precipitate is carried out behind hot-rolled step.Certainly, can generate thin precipitate by the speed of cooling of control steel band after hot rolling.In this case, it is just dispensable in the step of back to be used for generating the heat treated of thin precipitate.
For the particle diameter in cooling stages generation suitable proportion after hot rolling is 2 μ m or littler precipitate, carry out in the refrigerative process at hot rolled strip, hot rolled strip is carried out air cooling, and optionally carry out water cooling, water-cooled condition is to satisfy the above-mentioned treatment condition of separating out.
It is 1.0mm or thicker stainless steel plate that the present invention is particularly conducive to thickness, though the shape of product made from steel be there is no particular restriction.Certainly, characteristics of the present invention even be lower than the stainless steel plate of 1.0mm or by processing or be welded into by the goods that stainless steel plate is made, also can realizing of certain shape for thickness.
Several steel that will have composition as described in Table 1 melt in the vacuum oven of 30kg, and are cast into the flat board that thickness is 40mm, and 1250 ℃ of following soaking 2 hours, it was thick to be rolled into 4.5mm, uses water cooling then.In table 1, No. 8 No. 9 corresponding to SUS436 corresponding to SUS409.
Table 1: stainless chemical constitution
| Grade of steel | Alloy element (quality %) | Annotate | |||||||
| C | Si | Mn | Ni | Cr | Nb | N | Other | ||
| 1 2 3 4 5 6 | 0.007 0.025 0.012 0.014 0.011 0.009 | 0.85 0.51 0.93 0.31 0.52 0.26 | 0.81 0.75 1.08 0.34 0.43 0.99 | 0.07 0.11 0.11 0.12 0.13 0.13 | 8.63 12.02 14.47 17.85 19.52 18.57 | 0.35 0.58 0.40 0.42 0.41 0.79 | 0.006 0.010 0.011 0.010 0.015 0.007 | Cu：0.06 - Cu：0.10 Mo：0.52 Cu：0.49 Cu：0.24，Mo：2.94 | Inventive embodiments |
| 7 8 9 | 0.010 0.014 0.007 | 0.22 0.37 0.53 | 0.98 0.31 0.44 | 0.11 0.12 0.08 | 18.43 17.92 11.15 | 0.97 - - | 0.011 0.012 0.005 | Cu：0.23，Mo：2.24 Ti：0.18，Mo：1.03 Ti：0.21 | Comparative example |
Underscore numerical value exceeds the scope of the invention
It is 2.0mm that steel band after each hot rolling is cold-rolled to thickness, carries out final annealing under the condition as shown in table 2 then.
Table 2: create conditions
| Embodiment number | Grade of steel | The heating of hot rolled strip | Cold rolling (mm) | The heating of cold-rolled steel strip | Final annealing | Annotate | |||
| Temperature (℃) | Second | Temperature (℃) | Second | Temperature (℃) | Second | ||||
| 1 2 3 4 5 6 7 8 9 10 11 | 1 2 3 2 2 2 2 2 4 5 6 | 700 700 700 800 - - - 700 - - - | 3600 3600 3600 3600 - - - 10 - - - | 4.5/2.0 4.5/2.0 4.5/2.0 3.5/1.5 4.5/2.0 4.5/2.0 4.5/2.0/0.8 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 | - - - - 850 700 700 - 700 700 700 | - - - - 10 36000 36000 - 3600 3600 3600 | 900 1060 1040 1040 1040 1040 1040 1040 1100 1080 1000 | 10 10 | Inventive embodiments |
| 10 10 10 10 10 60 10 10 10 | |||||||||
| 12 13 14 15 16 17 18 | 7 8 9 2 2 2 2 | - - - 1040 1040 - - | - - - 10 10 - - | 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 | 700 700 700 - 700 700 700 | 3600 3600 3600 - 3600 3600 3600 | 1040 1040 1040 1040 1040 850 1150 | 10 10 10 10 10 10 10 | Comparative example |
The test film that every kind of annealed steel plate is scaled off at room temperature carries out tension test.
Weigh by the resistates that the fundamental element except that precipitate is obtained after electrolytic dissolution, with to the annealed steel plate before annealing and other test film of scaling off afterwards test, detect the ratio of precipitate.
And then steel plate cut becomes 3/4 of original thickness, polishes then, and preparation is used for the test film of crystalline orientation.On (211) and (200) plane, measure the diffracted intensity of each test film by XRD, and on (211) and (200) plane, measure diffracted intensity in an identical manner by the directionless sample of powdered material preparation.Observed value is substituted the formula in (a), calculate as crystalline orientation exponential integrated intensity.
The processing characteristics of each steel plate is that calculate on the basis according to the average plastic strain ratio r of expression deep-draw ductile.Average answering property of plasticity is than being to be obtained by following tension test: along rolling direction L, respectively downcut the test film that as JIS#13B stipulate with the vertical horizontal T of direction L with direction L direction D at 45 on each steel band.Under JIS Z2254 (being entitled as " experiment with measuring of thin type metal sheet plastic strain ratio ") defined terms, each test film is imposed 15% single direction stretching prestrain, respectively along the plastic strain ratio r on L, T and the D aspect
L, r
TAnd r
DRatio calculation with thickness strain and horizontal strain.With calculation result r
L, r
TAnd r
DThe substitution following formula obtains average plastic strain ratio r peace intra-face anisotropy Δ r.
r＝(r
L+2r
D+r
T)/4
Δr＝(r
L-2r
D+r
T)/2
The toughness of every kind of steel plate is according to but shellfish (Charpy) shock test (being entitled as " impact experiment of metallic substance ") detection under-75 to 0 ℃ of V-notch of JIS Z2242 regulation.Obtain the ductility-brittle transition temperature of every kind of steel plate by the Charpy impact test value.
Test-results is as shown in table 3 below.Should be understood that, the processing characteristics of the ferritic stainless steel of embodiment 1-11 is better than comparative example 15, this is because have bigger plastic strain ratio r, and the ratio of the precipitate before final annealing and all remain in the suitable scope by the crystalline orientation that integrated intensity is represented.Its ductility-brittle transition temperature of each steel of embodiment 1-11 all is lower than-50 ℃,, the degree of brittle rupture can not take place in reality that is.These results confirm that precipitate has advantageously been controlled the crystalline orientation of the final annealing steel plate that improves processing characteristics.
Embodiment 12-14 demonstrates has the stainless result that the present invention forms.Embodiment 15-18 demonstrates stainless result, and described stainless steel has the defined composition of the present invention, but handles under different creating conditions.
The steel of embodiment 16 has relative better machining property, but because the Nb too high levels, toughness is relatively poor.Embodiment 13 and 14 steel have good toughness, but processing characteristics is not good, this be because, even before final annealing through separating out processing, but owing to lack Nb, integrated intensity fails to remain in the specified range.The steel of embodiment 15 is to handle but separate out according to the final annealing that is used for recrystallization comprising of routine to handle and make, and its processing characteristics is relatively poor.Although the steel of embodiment 16 has carried out separating out processing, because the recrystallization tissue that produces when hot rolled strip is heated, its processing characteristics also fails to improve.The steel plate toughness of embodiment 17 and 18 final annealing is relatively poor, because in embodiment 17, the final annealing temperature is lower, makes precipitate fully not to be dissolved in the steel matrix, and perhaps because in embodiment 18, the final annealing temperature is higher to make grain coarsening.
Table 3: form and create conditions to the influence of precipitate ratio and steel plate character
| Embodiment number | Grade of steel | Precipitate ratio (%) | Integrated intensity | r | Toughness | Annotate | |
| Before the final annealing | Behind the | ||||||
| 1 2 3 4 5 6 7 8 9 10 11 | 1 2 3 2 2 2 2 2 4 5 6 | 1.1 1.3 1.1 1.3 1.3 1.4 1.6 1.6 1.2 1.1 2.0 | 0.2 0.3 0.3 0.4 0.4 0.5 0.6 0.3 0.5 0.1 0.2 | 1.2 2.0 1.2 1.9 1.8 2.1 1.7 1.6 1.5 1.2 2.3 | ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ | ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ | Inventive embodiments |
| 12 13 14 15 16 17 18 | 7 8 9 2 2 2 2 | 3.0 0.1 0.1 0.3 1.2 1.3 1.2 | 1.1 0.1 0.1 0.3 0.3 0.8 0.3 | 2.9 1.0 0.9 0.9 0.9 1.4 0.9 | × × × × × ○ ○ | × ○ ○ ○ ○ × × | Comparative example |
The numeral of band underscore is outside the scope of the invention.
The r value is not less than 1.5 and is evaluated as zero, less than 1.5 be evaluated as *.
Toughness: ductility-brittle transition temperature is lower than-50 ℃ and is evaluated as zero, be higher than-50 ℃ to be evaluated as *.
Embodiment 2
To have several steel of forming shown in the table 4 and melt in the vacuum oven of 30kg, and be cast into the flat board that thickness is 40mm, 1250 ℃ of following soaking 2 hours, it was thick to be rolled into 4.5mm, uses water cooling then.In table 4,1-9 number is steel of the present invention, and No. 10 No. 11 No. 12 corresponding to SUS436 corresponding to SUS409 in order relatively to use steel.
Each hot rolled strip is cold-rolled to 2.0mm, under the condition shown in table 5 (embodiments of the invention) and the table 6 (comparative example), anneals then.
Table 4: stainless composition
| Grade of steel | Alloy element (quality %) | Annotate | |||||||
| C | Si | Mn | Ni | Cr | Nb | N | Other | ||
| 1 2 3 4 5 6 7 8 9 | 0.007 0.025 0.012 0.014 0.011 0.009 0.009 0.009 0.004 | 0.85 0.51 0.93 0.31 0.52 0.30 0.26 0.52 0.12 | 0.81 0.75 1.08 0.34 0.43 0.21 0.99 0.04 0.18 | 0.07 0.11 0.11 0.12 0.13 0.09 0.13 0.57 0.09 | 8.63 12.02 14.47 17.85 19.52 16.72 18.57 34.14 20.11 | 0.35 0.58 0.40 0.42 0.41 0.39 0.79 0.15 0.20 | 0.006 0.010 0.011 0.010 0.015 0.008 0.007 0.009 0.016 | Cu：0.06 - Cu：0.10 Mo：0.52 Cu：0.49 Cu：1.59 Cu：0.24，Mo：2.94 Ti：0.11，Al：0.13 Ti：0.07，Al：5.52 | Inventive embodiments |
| 10 11 12 | 0.010 0.014 0.007 | 0.22 0.37 0.53 | 0.98 0.31 0.44 | 0.11 0.12 0.08 | 18.43 17.92 11.15 | 0.97 - - | 0.011 0.012 0.005 | Cu：0.23，Mo：2.24 Ti：0.18，Mo：1.03 Ti：0.21 | Comparative example |
The numeral of band underscore exceeds scope of the present invention.
Table 5: of the present invention creating conditions
| Embodiment number | Grade of steel | The thermal treatment of hot rolled strip | Cold rolling (mm) | The thermal treatment of cold-rolled steel strip | Final annealing | |||
| Temperature (℃) | Second | Temperature (℃) | Second | Temperature (℃) | | |||
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | 1 2 3 3 3 3 3 3 3 4 5 6 7 8 9 | 700 700 700 600 - - - - 700 - - - - - - | 10 10 10 60 - - - - 10 - - - - - - | 4.5/2.0 4.5/2.0 4.5/2.0 3.5/1.5 4.5/2.0 4.5/2.0 4.5/2.0/0.8 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 | - - 600 - 650 500 600 - - 600 600 600 600 600 600 | - - 10 - 10 36000 10 - - 10 10 10 10 10 10 | 900 1060 1040 1040 1040 1040 1040 1040 1040 1000 1030 1020 1100 1080 1000 | 10 10 10 10 10 10 10 10 60 10 10 10 10 10 10 |
Table 6: be used for correlated creating conditions
| Embodiment number | Grade of steel | The thermal treatment of hot rolled strip | Cold rolling (mm) | The thermal treatment of cold-rolled steel strip | Final annealing | |||
| Temperature (℃) | Second | Temperature (℃) | Second | Temperature (℃) | Second | |||
| 16 17 18 19 20 21 22 23 24 25 26 27 | 10 11 12 3 3 3 3 3 3 3 3 8 | - - - 1040 1040 900 400 - - - - - | - - - 10 10 10 3600 - - - - - | 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 4.5/2.0 6.0/2.0 | 600 600 600 - 600 - - 300 900 600 600 650 | 10 10 10 - 10 - - 36000 10 10 10 10 | 1040 1040 1040 1040 1040 1040 1040 1040 1040 850 1150 1100 | 10 10 10 10 10 10 10 10 10 10 10 600 |
The numeral of band underscore exceeds scope of the present invention.
The test film that steel band after every kind of annealing downcuts at room temperature carries out tension test.
In the mode identical with embodiment 1, other test film that steel band is carried out downcutting before and after the final annealing detects the ratio and the crystalline orientation of its thin precipitate, but crystalline orientation is represented by the integrated intensity of formula (b) definition.
The processing characteristics of each steel plate and toughness are also estimated by the mode identical with embodiment 1.
All results are shown in table 7 (embodiments of the invention) and table 8 (comparative example).
After comparing, table 7 and table 8 can find out, the steel of embodiment of the invention 1-15 is compared with the steel of embodiment 19 by the ordinary method manufacturing, has anisotropy (Δ r) in more excellent processing characteristics r and the lower plane, because the crystalline orientation (being represented by integrated intensity) of precipitate ratio in the steel matrix before final annealing and steel plate remains in the suitable scope.Each its ductility-brittle transition temperature of steel of embodiment 1-15 all is lower than-50 ℃,, the degree of brittle rupture can not take place in reality that is.These results confirm that thin precipitate is obviously influential to improving processing characteristics.
Embodiment 16-18 has shown and has relatively used stainless result.Embodiment 19-26 demonstrates has the defined composition of the present invention, but difference create conditions down processing and obtain relatively use stainless result.
The steel of embodiment 16 has relative good processing properties, but because excessive N b content, toughness is relatively poor.The steel of embodiment 17 has good toughness, but processing characteristics is relatively poor, even carrying out separating out processing before the final annealing, owing to lack Nb, integrated intensity does not keep in the specified range.
Embodiment 19 and 20 steel processing characteristics fail to improve, even produced thin precipitate by separating out to handle, this is because hot rolled strip is being higher than that heating is deformed into the recrystallization tissue under 1040 ℃ the temperature outside the scope of the invention.Embodiment 21 and 24 steel have anisotropy in the relatively poor plane, and its integrated intensity exceeds the framework of the present definition, because they are heating under hot rolling or Cold Rolled Strip under the higher temperature, make the thin precipitate of excessive generation.Embodiment 22 and 23 steel processing characteristics are relatively poor, and its integrated intensity surpasses the framework of the present definition, because they are heating under hot rolling or Cold Rolled Strip under the lower temperature, makes that the generation of thin precipitate is insufficient.The steel of embodiment 25-27 also has relatively poor processing characteristics, because in embodiment 25, because final annealing temperature is lower, precipitate can not be dissolved in the steel matrix fully, in embodiment 26 the final annealing temperature too high and in embodiment 27 overlong time, make grain coarsening.
Table 7: the stainless character of the present invention
| Embodiment number | Grade of steel | Precipitate ratio (%) | Integrated intensity | r | Δr | Toughness | |
| Before the final annealing | Behind the | ||||||
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | 1 2 3 3 3 3 3 3 3 4 5 6 7 8 9 | 0.9 0.8 0.9 1.0 0.9 1.1 1.0 0.7 0.9 1.0 0.9 0.9 1.2 0.4 0.6 | 0.2 0.3 0.3 0.3 0.3 0.3 0.3 0.4 0.3 0.3 0.3 0.3 0.5 0.1 0.2 | 3.0 2.7 2.5 2.4 2.6 2.6 3.6 2.1 2.3 2.2 2.4 2.1 2.0 2.0 2.0 | ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ | ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ | ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ |
R:1.2 or be evaluated as zero greatlyyer, less than 1.2 be evaluated as *.
Δ r:0.5 or be evaluated as zero more for a short time, greater than 0.5 be evaluated as *.
Toughness: ductility-brittle transition temperature is lower than-50 ℃ and is evaluated as zero, be higher than-50 ℃ to be evaluated as *.
Table 8: relatively use stainless character
| Embodiment number | Grade of steel | Precipitate ratio (%) | Integrated intensity | r | Δr | Toughness | |
| Before the final annealing | Behind the final annealing | ||||||
| 16 17 18 19 20 21 22 23 24 25 26 27 | 10 11 12 3 3 3 3 3 3 3 3 8 | 2.2 0.1 0.1 0.3 0.9 1.8 0.3 0.2 1.4 1.0 0.9 0.8 | 1.1 0.1 0.1 0.3 0.3 0.4 0.2 0.2 0.4 0.8 0.3 0.3 | 1.8 1.4 1.6 1.0 1.3 1.0 1.9 1.8 1.0 2.1 1.7 1.9 | × × × × × ○ × × ○ ○ ○ ○ | ○ × × × × × ○ ○ × ○ × × | × ○ ○ ○ ○ ○ ○ ○ ○ × × × |
R:1.2 or be evaluated as zero greatlyyer, less than 1.2 be evaluated as *.
Δ r:0.5 or be evaluated as zero more for a short time, greater than 0.5 be evaluated as *.
Toughness: ductility-brittle transition temperature is lower than-50 ℃ and is evaluated as zero, be higher than-50 ℃ to be evaluated as *.
As mentioned above, the present invention has utilized the precipitate that produces in stage before the final annealing control action kou to crystalline orientation in the final annealing process, thereby a kind of ferritic stainless steel with excellent machinability can be provided.And then, can reduce anisotropy in the plane by ratio and the crystalline orientation of strictly controlling thin precipitate.
Even when steel plate is relatively thicker 1-2mm, good processing properties also can guarantee, and intrinsic character such as thermotolerance, erosion resistance and toughness can not demoted yet.Because have excellent character, the ferritic stainless steel that newly provides will be used for the wide industrial field, as the element of the exhaust system of automobile.
Claims (6)
1. ferrite stainless steel that has excellent machinability and have less anisotropy, it is characterized in that, described ferrite stainless steel is by the C of 0.03 quality %, the N of 0.03 quality %, the Si of 2.0 quality % at the most at the most at the most, the Mn of 2.0 quality % at the most, the Ni of 0.6 quality % at the most, the Cr of 9-35 quality %, the Nb of 0.15-0.80 quality % forms, all the other are iron and unavoidable impurities
It is 0.5 μ m or the littler metallographic structure that contains the Nb precipitate that described ferrite stainless steel also has particle diameter, and described precipitate is by being used for being orientated at final annealing process crystallization control by separating out to handle to produce and consume, and its ratio is no more than 0.5 quality %,
Described crystalline orientation is on the surface at 1/4 thickness place in the degree of depth, and the integrated intensity that is defined by formula (b) is not less than 2.0;
Integrated intensity=[I
(222)/ I
0 (222)]/[I
(200)/ I
0 (200)] ... (b)
Wherein, I
(222)And I
(200)Diffracted intensity on (222) and (200) plane of the described steel plate sample that expression is recorded by XRD, and I
0 (222)And I
0 (200)Represent the diffracted intensity on (222) and (200) plane of nondirectional sample.
2. ferritic stainless steel according to claim 1, it further comprises a kind of at least following: the Ti of 0.5 quality % at the most, the Mo of 3.0 quality % at the most, the Cu of 2.0 quality % and the Al of 6.0 quality % at the most at the most.
3. ferritic stainless steel according to claim 1, wherein, before final annealing, thin precipitate is that 0.4-1.2 quality % is distributed in the steel matrix with the overall proportion.
4. a manufacturing has excellent machinability and has the method for anisotropic ferrite stainless steel in the low plane, comprises the steps:
A kind of ferritic stainless steel is provided, it is by the C of 0.03 quality % at the most, the N of 0.03 quality % at the most, the Si of 2.0 quality % at the most, the Mn of 2.0 quality % at the most, the Ni of 0.6 quality % at the most, the Cr of 9-35 quality %, 0.15-0.80 the Nb of quality % forms, all the other are iron and unavoidable impurities;
To described stainless steel the 450-750 ℃ of heating of separating out that is no more than 20 hours; And
To described stainless steel at 900-1100 ℃ of final annealing that is no more than 1 minute.
5. the manufacture method of ferrite stainless steel according to claim 4, wherein, ferritic stainless steel further comprises a kind of at least following: the Ti of 0.5 quality % at the most, the Mo of 3.0 quality % at the most, the Cu of 2.0 quality % and the Al of 6.0 quality % at the most at the most.
6. the manufacture method of ferrite stainless steel according to claim 4, wherein, before final annealing, thin precipitate is that 0.4-1.2 quality % is distributed in the steel matrix with the overall proportion.
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| JP392911/2000 | 2000-12-25 | ||
| JP2000392912A JP4562281B2 (en) | 2000-12-25 | 2000-12-25 | Ferritic stainless steel sheet with excellent workability and method for producing the same |
| JP2000392911A JP4562280B2 (en) | 2000-12-25 | 2000-12-25 | Ferritic stainless steel with excellent workability and small in-plane anisotropy and method for producing the same |
| JP392912/2000 | 2000-12-25 | ||
| JP392911/00 | 2000-12-25 | ||
| JP392912/00 | 2000-12-25 |
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| JPS5129694A (en) | 1974-09-04 | 1976-03-13 | Kajima Corp | |
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| JPS56123327A (en) * | 1980-02-29 | 1981-09-28 | Sumitomo Metal Ind Ltd | Production of highly formable ferritic stainless steel sheet of good surface characteristic |
| FR2589482B1 (en) * | 1985-11-05 | 1987-11-27 | Ugine Gueugnon Sa | STAINLESS STEEL FERRITIC STEEL SHEET OR STRIP, ESPECIALLY FOR EXHAUST SYSTEMS |
| JPH0617519B2 (en) * | 1986-02-27 | 1994-03-09 | 日新製鋼株式会社 | Method for producing steel plate or strip of ferritic stainless steel with good workability |
| KR950003159B1 (en) * | 1989-03-17 | 1995-04-01 | 가와사끼 세이데쯔 가부시끼가이샤 | Method of making stainless steel sheet for exterior building constituent |
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| JP3152576B2 (en) * | 1995-01-19 | 2001-04-03 | 川崎製鉄株式会社 | Method for producing Nb-containing ferrite steel sheet |
| JPH08311542A (en) * | 1995-05-12 | 1996-11-26 | Nippon Steel Corp | Production of ferritic stainless steel sheet for deep drawing excellent in ridging resistance and small in anisotropy |
| JP3190825B2 (en) * | 1996-06-27 | 2001-07-23 | 川崎製鉄株式会社 | Ferritic stainless steel hot-rolled steel sheet excellent in corrosion resistance, formability and material uniformity, and method for producing the same |
| JP4562281B2 (en) * | 2000-12-25 | 2010-10-13 | 日新製鋼株式会社 | Ferritic stainless steel sheet with excellent workability and method for producing the same |
| JP4824857B2 (en) * | 2001-01-15 | 2011-11-30 | 日新製鋼株式会社 | Ferritic stainless steel sheet and manufacturing method thereof |
-
2001
- 2001-12-13 EP EP01129311A patent/EP1219719B1/en not_active Expired - Lifetime
- 2001-12-13 DE DE60105955T patent/DE60105955T2/en not_active Expired - Lifetime
- 2001-12-13 ES ES01129311T patent/ES2230227T3/en not_active Expired - Lifetime
- 2001-12-21 US US10/027,850 patent/US6673166B2/en not_active Expired - Lifetime
- 2001-12-24 KR KR1020010084112A patent/KR100799240B1/en active IP Right Grant
- 2001-12-25 CN CNB011369132A patent/CN1172017C/en not_active Expired - Lifetime
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2003
- 2003-10-28 US US10/695,185 patent/US7094295B2/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101903553B (en) * | 2008-01-28 | 2015-09-09 | 新日铁住金不锈钢株式会社 | The high-purity ferritic stainless steel of erosion resistance and excellent in workability and manufacture method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| US6673166B2 (en) | 2004-01-06 |
| US7094295B2 (en) | 2006-08-22 |
| US20020117239A1 (en) | 2002-08-29 |
| US20040084116A1 (en) | 2004-05-06 |
| CN1363710A (en) | 2002-08-14 |
| EP1219719A1 (en) | 2002-07-03 |
| DE60105955T2 (en) | 2005-10-06 |
| ES2230227T3 (en) | 2005-05-01 |
| DE60105955D1 (en) | 2004-11-04 |
| KR20020052993A (en) | 2002-07-04 |
| EP1219719B1 (en) | 2004-09-29 |
| KR100799240B1 (en) | 2008-01-29 |
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